(a) Field of the Invention
The present invention relates to a robot control method capable of making a robot effect various operations in accordance with optimum control conditions.
(b) Description of the Related Art
In a conventional robot having servomotors for actuating various axes of the robot and servo systems for driving the servomotors, the response characteristics of the servo systems to their respective inputs and the servo gains for determining control conditions of the robot, e.g., gains in the proportional, integrating and differentiating elements involved in the servo systems, are set such that the response characteristics of the servo systems may be optimum when maximum load is applied on the servomotors. Thus, the conventional robot is controlled in accordance with control conditions which are unchangeable.
Meanwhile, the robot is required to make various operations, and the load applied on the servomotors of the robot varies depending on kinds of the operations of the robot. Therefore, if the control conditions of the robot are determined so as to be best suited to the maximum load, as mentioned above, excessive driving force can be supplied to the servomotors in ordinary states (i.e., when the maximum load is not applied on the robot). The tendency is particularly conspicuous in the case of a direct drive type robot. Thus, in the conventional robot, the response characteristics of the servo systems and, in turn, the control conditions of the robot are not in conformity to load conditions other than the maximum load condition. As a result, disadvantages arise, for example, in that the outputs of the servo systems overshoot the inputs thereto and oscillate, which causes vibration of the robot.